Panel board and method of making same



March 16,1937.. F P, WOOD 2,073,894

PANEL BOARD AND METHOD OF MAKING SAME Filed Jan. 30, 1936 Parenteel Mu. 1c, 11937 PATENT osi-ICE 2.01am. n PANEL noAan AND ME'rnon or MAKING Y l sAME Y Frederick r. wana', Adrian, Mich., signora Simplex Paper Corporation, Adrian, Mich., a corporation of Michigan Application .mmm so, 193s, serai N0. 61,505

13 Claims.

An object of this invention is to provide a panelboard which is relatively' hard 'and still and of nearly equal strength in all directions, which is highly water-resistant, and which does 5 not warp, twist, swell or'shrink to any appreciable degree under widely different conditions v of temperature or humidity.

Another object of this invention is to a method of making such a panelboard.

Another object of this invention is to provide an improved waterproof asphalt board which is sightly in appearance and particularly adapted for use in the automobile industry, as a panelboard, and the like, and which is economical to manufacture with present equipment.

These and other objects, as will hereinafter appear, are accomplished by this invention which is fully described in the following specication provide and shown in the accompanying drawing, in'

which- Figure 1 is adiagrammatic view showing mechanism for coating a ber paper which is the rst step in making the panelboard;

Fig. 2 is a greatly enlarged transverse section through a sheet of ber paper coated by the apparatus of Fig.' 1;

Fig. 3 is a diagram of mechanism for asl 8, 1932, and Serial No. 21,762, filed `May 16, 1935.V

Generally speaking, the panelboard is composed of two,` three, four or more sheets of paper each of a thickness of .016" or more (preferably .0026" or .0032" which I am now using, or more) of a kraft pulp or the like. This is so made that the fibers of the paper which are nearly pure cellulose, are running nearly equally in all directions, each. sheet being separately treated to render it water-resistant, and the sheets assembled with a suitable adhesive between them. For this purpose the paper may be made of 50 kraft sulphate pulp or other chemical pulp, or

ber on a Fourdrinier paper machine. Paper so made possesses a strength and-rigidity in a direction across the grain of two-thirds or more of the strength with the grain, (i. e., the direction of travel of the sheet through the paper 4 er, with a suitable size, such as a soluble resin soap, alum being added to change the soluble soap into an insoluble soap in a well known manner. This soap is precipitated on the sides and ends of the individual cellulose iibers, while still in the beater, by the addition of an acid. The amount of size added is suilcient to make the paper hard sized. In this condition, the resulting paper is water-resistant but will not re sist expansion or contraction under verying moisture conditions. If the kraft paper is not properly sized, the panelboard made from it, as will later be explained, will absorb too much water.

This kraft pulp paper has one essential for this d purpose, i. e., it is a single layer of fibers, whereas in a paper made on a cylinder machine, there are as many'layers as there are cylinders in use, the fibers of one layer being discontinuous from the fibers of the next adjacent layer. Conse quently the hot liquid filler, as asphalt or resin, is able to` penetrate from one layer to the next but slowly in the case of the paper made on the cylinder. machine, whereas it penetrates rapidly into the kraft paper because the bers are continuous, and are relatively long.

`In Fig. 1 is shown a mechanism for treating a single sheet of pulp paper, for this purpose Vwith a suitable waterproofing material. In this mechanism the sheet of pulp paper to be treated is unwound from a reel A, passes over steam-heated rolls Il and down under rollers i3 and I4 in a tank I5 so as to pass beneath the surface of molten asphalt I6 which is preferably heated in any well known manner, as by a furnace thereunder, at atemperature of about 400 to 425 F. Air and water in the paper are expelled and are carried off by the pipe l2 which leads to a stack. The tank has sliding covers I 5*.

'Ihis tank is suiciently long to give the molten asphalt time to penetrate well into the ber ofk the paper which preferably is traveling 180 to 225 per minute. For some purposes, the paper maybe saturated throughout by the asphalt,

When the paper treated in this way leaves the tank of asphalt, it is nearly free from water, is brittle, and is preshrunk and it passes out between two pressure rolls l1, where it is squeezed fairly dry of excess asphalt. Enough asphalt remains, however, to make the surface of rthe' sheet very shiny as it leaves the squeezing rolls. If this sheet is held in the air for a few seconds, this surface asphalt is rapidly drawn into the sheet. I accordingly place rolls I8, I9 some distance from the rolls Il so as to provide a stretch 20 long enough for this absorption to take place. The paper is then cooled by the water-cooled rolls I 8, I9 and is wound up on a roll B. 'This paper is bone dry and avid for moisture which must be added to it in some way in order to restore the'necessary toughness to the sheet. If left in theair for some time, it will absorb 7% to 8% of its weight in moisture but will take it up in the roll but slowly through the edges.

To make a panelboard, two or more sheets of this pulp are then secured together with a suitable waterproof adhesive between them, as many sheets as desired being used to make any desired thickness of board. The adhesive used contains suiilcient water to give the panelboard a normal moisture content of '7% to 8%, thereby returning the toughness to the paper. This water is absorbed by the board even when asphalt has passed all the way through.

To make this panelboard, two such rolls of paper B', B2 are mounted in the mechanism shown in Fig. 3. 'I'he sheet from B' is led over a roller 23 between rollers 24, 25, thelatter dipping into a bath of a suitable waterproof adhesive 26. For this purpose I prefer to use a cement composed of nearly equal parts of rubber latex and starch paste containing water as a solvent. The starch has the jelling properties removed but is not dextrinized. Less rubber lmay be used if desired. Ammonia present in the rubber latex keeps it in a state of emulsion. 2% to 3% of a soft asphalt emulsiiied with silicate of soda, clay, etc., adds greatly to the strength of the cement. The sheet so coatedwith cement is brought into juxtaposition with the sheet from the roll B2 and the two sheets are firmly pressed together as' they pass through between pressing rolls 21, after which they are preferably passed through cutters 28 which cut the sheet 29 into panelboard rectangles 29a which are preferably stacked on a truck 30. A top plate or cover 3| is placed on top of the pile and clamped down by means of tightening screws 32 and nuts 33.

When the sheet emerging from the asphalt bath I6 passes the squeezing rollers I 1, it may be completely saturated with asphalt or it may possess a cross section like that shown in Fig. 2

in which there may be an unsaturated or semisaturated central core 50 with infiltration layers Il," of hard asphalt. 'I'he fibers of the sheet assembled as they are on a Fourdrinier machine run in all directions and many of the fibers 43 extend from points outside the asphalt to pointsV well within the asphalt. When the sheet emerges from the bath of asphalt, the heat of the asphalt has expelled substantially all of its moisture, so that the sheet emerges in a very dry state.

When the waterproof starch adhesive isqapplied, it preferably contains just suicient water to return the iiber sheet to a normal moisture content. The protruding liber ends I3 are buried in the waterproof starch adhesive 26,* (Fig. 4)- and hence in intimate contact therewith, and it is my theory that moisture, probably because of the partial sealing effect of the asphalt, and resin size passes very slowly along or through these fibers by capillary attraction, and as it doesso carries with it the waterproof starch adhesive. This is possible because of the fact that the water and air normally within the cells of the ilbers themselves has been expelled by the heat treatment so that the voids thus created permit the water to be sucked in. The result is that the adhesive is drawn well into the body of the sheetv along or'through these fibers as through minute tubes, and as it slowly sets rmly cements the two sheets together. 'I'herubber latex then serves to exclude moisture so that even though the panelboard is placed in water for a considerable period of .time after it has once set, very little softening of the adhesive takes place. In addition, the latex adds some adhesive action. An adhesive such as casein and lime, albumen and lime, or any other water-soluble adhesive containing some waterproofing agent may be used instead of the latex starch mixture, but most of these are more costly.

When the sheets 29 are first assembled the cement has not yet had time to set, consequently the sheets composing the panelboard can be read-A ily separated. After it has been held clampe'd on the truck for a period of four to six hours, the cement becomes thoroughly set and the sheets can no longer be separated on the central plane. This panelboard can be readily pressed into various shapes just after it emerges from the cutters 29 and before it has had time to set. After pressing, it should be left in the desired form until the cement has set, as previously explained, after which it will retain that form. By raising this moisture content to 10-12% the panelboard can be kept in a moist room for months before pressing. On pressing, it dries and sets as before.

For certain purposes the central core may be practically saturated with asphalt and stilll take up very considerable quantities of moisture from the cement so as,to .be quite tough because of a return thereto of a normal moisture content.

When panelboards are thus made they have a normal moisture content of '7-8% by weight so that these panels can be taken into regions having very widely different humidity without any tendency of the panelboard to shrink, expand, warp, buckle or cockie' even when the panelboard is immersed in water for several hours or subjected to very dry atmosphere for long periods.

It is found in practice that a much harder asphalt may be used to advantage. For example, an asphalt having a melting point of F. and a penetration point of 4 has proved highly satis- The limits set out earlier are intended to mark approximately the softer limits oi' asphalt for good results in the panelboard.

In actual practice. this panelboard has been found to possess unusual strength and rigidity in all directions, to be highly water-resistant, and to be little affected by changes of temperature ,and humidity, so that it is particularly suited for use as a panelboard for automobiles, and the like. For such a purpose this board can be cut and punched to size, and in this condition can be shipped over long distances and stored for long periods and later assembled without the danger thatit will not nt the parts with which it was intended to be assembled. v

This panelboard has a. surface which readily adapts it topainting, embossing in imitation of leather, and the like, directly thereon, or cloth trim may be secured thereon by means of a suitable adhesive without danger of warping or of the asphalt coming through the cloth, since it is my theory that the asphalt is trapped and held within the interstices between the bers, so that the hard and brittle asphalt becomes, as it were,

a permanent constituent of the structure of the panelboard and will not exude or release therefrom under any conditions encountered in service.

For certain purposes, the hard asphalt may be replaced by a hard brittle resin, or coal tar pitch, or Wood pitches, either natural or synthetic, which is applied molten in the same way as the asphalt. The resulting panelboard will take the same adhesive as for asphalt and will be moisture-proof in'about the same degree. The cost is considerably more. The resin lled sheet may be 4given any desired color, or it may be printed to resemble a wood grain. The outer layer may be thus treated while the other layers are lled with asphalt. A

While I prefer to use a beater sized pulp sheet, it may, if desired, be tub sized. Paraffln may also be used as a tub size after which the sheet is treated with molten parafn or'resin as before.

For the sake of illustration, I have shown two sheets of pulp, but in actual practice, I nd it advantageous to use three sheets and apply the cement to both sides of the central sheet, the two uncoated outer sheets then being pressed into contact with the central sheet. For certain purposes, I also precut the sheets and turn one sheet so that its grain runs at right angles to that of another sheet.

The ends of the fibers protruding beyond the surface of the panelboard may be noticeable and, if desired, these may be dyed any color as by means of an alcohol soluble dye; The outer surface may also be coated with a waterproof material, such as tung oil, to further assist in special cases in preventing the ingress and egress of moisture.

I claim:

1. A product in sheet form which is highly resistant to physical change in a Wide range of temperature and humidity conditions, comprising a sheet of sized fibre pulp consisting of a singly formed layer of fibres of nearly pure cellulose disposed substantially uniformly in all directions, said sheet being lpartially impregnated with asphalt having a melting point of not less than 140 F. and a penetration point of not over 22, the surface fibres of the sheet extending beyond the body of. asphalt, whereby said sheet may be cemented to an adjacent surface.

2. A. panelboard comprising two superposed sheets, at least one of said sheets being resistant to physical changefin a Wide range of temperature and humidity conditions,`said sheet being composed of sized fibre pulp consisting of a singly formed layer of bres of nearly pure cellulose disposed substantially uniformly in all directions, said sheet being impregnated with asphalt having a melting point of not less than 140 F. and a penetration point of not over 22, and an adhesive uniting the surface fibres of the superposed sheets.

3. A panelboard comprising two superposed sheets, each sheet `being resistant to physical change in a wide-range of temperature and humidity conditions, each sheet being composed of sized fibre pulp consisting lof a singly formed layer of bres of nearly pure cellulose disposed substantially uniformly in all directions, each sheet being impregnated with asphalt having a melting point of not less than 140 F. and a penetration point of notvover 22, the surfaces of the sheets having protruding libres, and an adhesive uniting adjacent surfaces of the sheets, said adhesive extending into the body of the sheets through said protruding surface fibres;

4. A panelboard comprising two superposed sheets, each sheet being resistant `to physical change in a Wide range of temperature and humidity conditions, each sheet being composed of sized fibre pulp consisting of a singly formed layer of fibres of nearlypure cellulose disposed substantially uniformly inl all directions, each sheet being impregnated with asphalt having a melting point of not less than 140 and a penetration point of not over 22, th'e surfaces of the sheets having protruding bres, and a waterproof starch adhesive uniting adjacent surfaces of the sheets, the starch of said adhesive extending into the body of the sheets through said protruding surface fibres.

5. The method of making a product in sheet form which is highly resistant to physical change in a wide range of temperature and humidity conditions which comprises impregnating a sheet of sized bre pulp with molten asphalt,

then simultaneously compressing the bres 'of `the sheet and removing the excess asphalt therefrom, then allowing the fibres of the sheet to expand for a predetermined period of time to draw the surface layers of asphalt into the body of the sheet and cooling the sheet.

6. The method of making a product in sheet form which is highly resistant to physical change in a wide range of temperature and hu-- midity conditions which comprises Vpassing a sheet of sized bre pulp through a bathof molten, hard and brittle asphalt for a period of time sufficient to simultaneously impregnate the sheet and remove substantially the entire normal moisture content of the sheet, then passing the sheet between squeezing rolls to simultaneously compress the iibres of the sheet and remove excess asphalt therefrom, then allowing' the fibres of the sheet to Vexpand and the sheet to cool for a predetermined period of time to draw the molten asphalt into the body of the sheet, and then finally adding sufficient moisture to the sheet to restore its normal moisture content.

'7. The method of making a product in sheet form which is highly resistant to physical change in a Wide range of temperature. and humidity conditions which comprises passing a sheet of sized iibre pulp through a bath of molten, hard and brittle asphalt for a period of time suiicient to simultaneously impregnate the sheet and remove substantially the entire normal moisture content of the sheet, then passing the sheet between squeezing rolls to simultaneously compress the bres of the sheet and remove excess asphalt therefrom, then allowing I draw the molten asphalt into the body oi' 'the -asphait havinga melting point, of not less than 140` F. and a penetration point of not over 22 at a temperature and for a period of time sumcient to dehydrate the sheet, simultaneously compressing the fibres of the sheet and removing the excess asphalt therefrom as the sheet leaves the molten asphalt, and suspending the sheet in the air for a predetermined period to permit the sheet to draw the molten surface asphalt into the body of the sheet.

9. The method of making a product in sheet form which is highly resistant to physical change in a Wide range of temperature and humidity conditions which comprises impregnating a sheet of sized fibre pulp having the fibres disposed nearly uniformly in all directions with molten asphalt having a melting point of not less than 140 F. and a penetration point of not over 22 at a temperature and for a period of time sufiicient to dehydrate the sheet, simultaneously compressing the fibres of the sheet and removing the excess asphalt therefrom as the sheet leaves the molten asphalt, suspendingthe sheet in the air for a predetermined period to permit the sheet to draw the molten surface asphalt into the body of the sheet, and then cooling the sheet.

10. The method of making a product in sheet form which is highly resistant to physical change in a wide range of temperature and humidity conditions which comprises impregnating a sheet of sized fibre pulp having the fibres disposed nearly uniformly in all directions with molten asphalt having a melting point of not less than 140 F. and a penetration point of not jover 22 at a temperatureand for a period of time sumcient to dehydrate the sheet, simultaneously compressing the fibres of the sheet and removing the excess asphalt therefrom as the sheet leaves the molten asphalt, suspending the sheet in the air for a predetermined period to permit the sheet to draw the molten surface asphalt into the body of the sheet, and adding suiiicient moisture to the sheet to restore its normal moisture content.

11. The method or making a product in sheet' form which is highly resistant to physical change in a wide range of temperature and himidity conditions which comprises impregnating a sheet of sized fibre pulp having the bres disposed nearly uniformly in all directions with molten asphalt having a melting point of not lessv than 140 F. and a. penetration point of not over 22 at a temperature and for a period of time sufiicient to dehydrate the sheet, simultaneously compressing the fibres of the sheet and removing the excess asphalt therefrom as the sheet leaves the molten asphalt, suspending the sheet in the air for a predetermined period to permit the sheet to draw the molten surface asphalt into the body of the sheet, applying an adhesive'containing water to one surface of the sheet to restore the normal moisture content to said sheet, and bringing a second sheet into intimate contact with the adhesive on the first sheet.

l2. The method of making a product in sheet form which is highly resistant to physical change in a wide range of temperature and humidity conditions which comprises impregnating a sheet of sized fibre pulp having the fibres disposed nearly uniformly in all directions with molten asphalt having a melting point of not less than '140 F. and a penetration point of not over 22 at a temperature and for a period of time suiilcient to dehydratel the sheet, simultaneously compressing th'e fibres of the sheet and removing the excess asphalt therefrom as the sheet leaves the molten asphalt, suspending the sheet in theair for a predetermined period to permit the sheet to draw the molten surface asphaltI into the body of the sheet, applying an adhesive containing water to one surface of the sheet, bringing a second sheet into contact with the adhesive on the first sheet, pressing the sheets together, and applying pressure to the sheets until the adhesive sets.- 1 Y 13. The method of making a product in sheet form which is highly resistant to physical change in a wide range of temperature and humidity conditions which comprises impregnating a sheet of fiber pulp in a bath of molten material which renders the sheet water-resistant, said impregnating being done at a temperature and for a period of time sufficient to remove substantially all the moisture from the sheet, removing the excess molten material, applying an adhesive 'containing water to one surface of the dehydrated sheet, said water also restoring the normal moisture content of the dehydrated sheet, bringing a second sheet into contact with the adhesive layer onthe first sheet, and pressing the sheets together.

FREDERICK P. WCOD. 

